1. Field of the Invention
The present invention relates to a passive matrix bistable liquid crystal display system, and more particularly to a color passive matrix bistable liquid crystal display system and a method for driving the same.
2. Description of the Related Art
FIG. 1 is a schematic block diagram of the conventional color passive matrix bistable liquid crystal display device, which includes a lower substrate 100, a plurality of data electrodes 101 aligned in parallel, a plurality of scan electrodes 102 aligned in parallel, a data line driver 103, a scan line driver 104, a controller 102, a voltage source 106, a clock 107 and a plurality of blue light bistable liquid crystal cells (B) 108B, a plurality of green light bistable liquid crystal cells (G) 108G and a plurality of red light bistable liquid crystal cells (R) 108R. The data electrodes 101 are disposed on one surface of the lower substrate 100, and the scan electrodes 102 are perpendicularly stacked over the data electrodes 101. An intersection area of each of the scan electrodes 102 and each of the data electrodes 101 defines a sub-pixel area 108. For one respective scan electrode 102, the blue light bistable liquid crystal cells 108B, green light bistable liquid crystal cells 108G and the red light bistable liquid crystal cells 108R are sequentially sandwiched between one respective scan electrode 102 and the data electrodes 101 corresponding to the respective intersection areas thereof. In other words, for the conventional color passive matrix bistable liquid crystal display device, the liquid crystal cells of same color are aligned in a direction perpendicular to the scan electrodes 102. The data line driver 103 electrically connects with each of the data electrodes 101 to provide addressing data voltages to the data electrodes 101. The scan line driver 104 electrically connects with each of the scan electrodes 102 to provide scan driving voltages to the scan electrodes 102. The controller 105 is used to control the transmissions of the addressing data voltages of the data electrodes 101 and the scan driving voltages of the scan electrodes 102. The data voltages of the image signals are sequentially transmitted to the controller 105 through the voltage source 106 and the clock 107. Then, the controller 105 controls the scan line driver 104 to sequentially scan the scan electrodes 102. When the respective scan electrode 102 is scanned, the controller 105 controls the data line driver 103 to transmit the addressing data voltages to the data electrodes 101 to write the sub-pixel data into the corresponding sub-pixels.
FIG. 2 is an electro-optical graph of a known red light bistable liquid crystal, green light bistable liquid crystal and blue light bistable liquid crystal, and FIG. 3 is an electro-optical graph of another known red light bistable liquid crystal, green light bistable liquid crystal and blue light bistable liquid crystal. In view of FIG. 2 and FIG. 3, it can be seen that the scan driving voltages of the bistable liquid crystal cells of different illuminating colors are different, in which the scan driving voltage of the red light bistable liquid crystal cells is lowest, while the scan driving voltage of the blue light bistable liquid crystal cells is highest. In terms of the pixel arrangement of the conventional color passive matrix bistable liquid crystal display device, the respective scan electrode 102 corresponds to the liquid crystal cells of different illuminating colors. When the respective scan electrode 102 is scanned, the liquid crystal cells of different illuminating colors corresponding thereto are provided with the same scan driving voltage. As such, the pixel arrangement and driving method of the conventional color passive matrix bistable liquid crystal display device can not meet the demand that the liquid crystal cells of different illuminating colors have different scan driving voltages.
Taking FIG. 3 as an example, the highest driving voltages of the data electrodes with respect to the red light, green light and blue light liquid crystals are different, i.e. the voltage levels of the data electrodes respectively corresponding thereto are different. As to the conventional driving method, the data electrodes 101 are divided to three groups, when the respective scan electrode 101 is scanned, three respective voltage levels are provided to the corresponding data electrodes 101 to satisfy the demand that the liquid crystals of three different illuminating colors have different voltage levels. It is necessary to develop additional addressing circuits to provide respective addressing voltages to the liquid crystals of different illuminating colors, and that makes the circuit design of the data line driver 103 become more complicated. The conventional color passive matrix bistable liquid crystal device needs to be improved to alleviate the above drawbacks.